In the motor vehicle industry, there is an increasing demand for the reduction of the weight of motor vehicle components, with the aim of reducing fuel consumption and exhaust emissions. In order to reduce the overall weight of the wheel, and in particular of the rotating part of the wheel, hub bearing assemblies having a rotatable flanged ring composed of two different materials, joined together in a single piece, have been proposed in recent years. In these rings, a tubular core made of a first material having a high toughness, such as bearing grade steel, forms the raceways; a second, lightweight material, such as a lightweight metal, forms the remaining part of the ring, including an outer flange for mounting the wheel.
In some cases, the connection between the steel core and the lighter flange is provided by a positive connection. These connections do not always prove to be durable over time, above all after prolonged use. In fact, the different coefficients of thermal expansion of the steel and of the aluminum tend to cause separation of the two materials. In other cases, the connection is made by overmolding or casting the lightweight material, for example an aluminum alloy, on the tubular steel core. To avoid or limit relative movements between the two materials, in the rings of this type the two materials are joined by interface surfaces having a complex shape, in order to realize undercuts which act like joints between the two materials. See, for example, patent publication WO 2008/147284 A1. The production costs for the rings realized by this technique are rather high.